This invention relates to the conversion of chemical energy to electrical energy, and more particularly to a new and improved construction for lithium-iodine cells and method of making the same.
One area of use of the present invention is in providing electrical power safely to inacessible devices in the human environment, for example to an implanted cardiac pacemaker, although the principles of the invention can be variously applied. Several types of batteries for implantable cardiac pacemakers have been proposed but heretofore all have certain limitations. Recently a lithium-iodine cell has been proposed which advantageously has an open circuit voltage about twice that of the mercury cell, does not generate gas during operation, and has a non-corrosive electrolyte.
Several problems can arise in the manufacture or assembly of lithium-iodine cells. A cell has been proposed including a lithium anode and a cathode comprising a charge transfer complex of an organic donor component and iodine. In a recently developed method for making such a cell, the organic-iodine complex is introduced to a casing, which includes the remaining cell components, in the form of a pourable tar-like or viscous substance which may be heated to an elevated temperature. Observation of such cells over prolonged tests have indicated that in some instances the cell impedance and the rate of impedance buildup on discharge is quite variable. In other instances an abnormally high impedance buildup has been observed.